Fixer inks for use with ink jet inks

ABSTRACT

The disclosure provides an ink set containing an ink jettable ink and an ink jettable fixer ink having: an aqueous colorant containing ink jettable ink; and a fixer ink having: (i) a multivalent metal salt, wherein the metal is selected from the group consisting of divalent metal ions, trivalent metal ions, and mixtures thereof; and (ii) a salt stable, water soluble, predominantly non-ionic, polymeric binder selected from the group consisting of a polyurethane having an ethylene oxide unit, and a methoxylated carboxylated polyallylamine; wherein the polymeric binder is substantially non-reactive with the colorant. The colorant contains a dye, a self dispersed pigment or a pigment dispersion. These inks have enhanced coloristic and durability properties.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

This disclosure relates to aqueous dispersions, and in particular tofixer inks for use with ink jet inks and methods of printing substrates.

2. Description of Related Art

Ink jet printing is a non-impact printing process in which droplets ofink are deposited on a substrate, such as paper or textile, to form thedesired image. The droplets are ejected from a printhead in response toelectrical signals generated by a microprocessor.

Most inkjet printers are equipped with an ink set comprising two or moredifferent inks and are able to print black text and multicolor images.Typically, an ink set will comprise at least a cyan, magenta and yellowcolored ink and a black ink (CMYK ink set).

For printing text, it is desirable for the black ink to have highoptical density. For this purpose, a pigment colorant is mostadvantageous, especially a carbon black pigment. A pigment colorant isnot soluble in the ink vehicle and must be treated in order to cause itto remain dispersed and jet properly. To effect dispersion stability,pigments are commonly treated with dispersants, and a wide variety ofsuch materials have been disclosed. Especially effective are blockcopolymer dispersants which are described, for example, in U.S. Pat.Nos. 5,085,698, 5,519,085, 5,272,201, and 5,648,405. Amphoteric(sometimes referred to as polyampholyte) dispersants, i.e., dispersantscontaining moieties capable of reacting with acidic and basic reagents,for improved dispersion stability, have also been described. Forexample, U.S. Pat. No. 5,648,405 discloses an amphoteric dispersantformed of MAA/DMAEMA/BZMA random copolymer.

Typically substrates onto which images are printed are porous, eg. Paperor textile, and the printed image has a tendency to be absorbed into thesubstrate resulting in an image that has lower optical density. It isdesirable for the image to sit on the surface of the substrate toimproves its optical density, but it is also a requirement that thisimage be held in place to minimize or eliminate ink smear.

Despite the successful inkjet inks and print methods presentlyavailable, there is still a need for ink jet printed images having goodoptical density in combination with improved smear resistance.

SUMMARY OF THE DISCLOSURE

In a first aspect, the disclosure provides an ink set for ink jetprinting, comprising:

-   -   an aqueous colorant containing ink jet ink;    -   a fixer ink comprising:        -   (i) a multivalent metal salt, wherein the metal is selected            from the group consisting of divalent metal ions such as            Ga²⁺, Cu²⁺, Ni²⁺, Mg²⁺, Zn²⁺ and Ba²⁺, trivalent metal ions,            such as Al³⁺, Fe³⁺ and Cr³⁺, and mixtures thereof; and        -   (ii) a salt stable, water soluble, predominantly non-ionic,            polymeric binder selected from the group consisting of a            polyurethane comprising an ethylene oxide unit, and a            methoxylated carboxylated polyallylamine; wherein the            polymeric binder is substantially non-reactive with the            colorant.

The colorant comprises a dye, a self dispersed pigment or a pigmentdispersion. By ‘polymeric binder is substantially non-reactive with thecolorant’ it is meant that the solution of the salt stable, watersoluble, predominantly non-ionic, polymeric binder does not coagulate(gel) or precipitate when mixed with the ink.

In a second aspect, the disclosure provides a method for printing asubstrate comprising:

(a) providing an ink set, comprising:

-   -   an aqueous colorant containing ink jet ink;    -   a fixer ink comprising:        -   (i) a multivalent metal salt, wherein the metal is selected            from the group consisting of divalent metal ions such as            Ga²⁺, Cu²⁺, Ni²⁺, Mg²⁺, Zn²⁺ and Ba²⁺, trivalent metal ions,            such as Al³⁺, Fe³⁺ and Cr³⁺, and mixtures thereof; and        -   (ii) a salt stable, water soluble, predominantly non-ionic,            polymeric binder selected from the group consisting of a            polyurethane comprising an ethylene oxide unit, and a            methoxylated carboxylated polyallylamine; wherein the            polymeric binder is substantially non-reactive with the            colorant;

(b) applying the ink jettable fixer ink to the substrate, and

(c) applying the aqueous colorant containing ink jet ink to thesubstrate.

These and other features and advantages of the present disclosure willbe more readily understood by those of ordinary skill in the art from areading of the following detailed description. It is to be appreciatedthat certain features of the disclosure which are, for clarity,described above and below in the context of separate embodiments, mayalso be provided in combination in a single embodiment. Conversely,various features of the disclosure that are, for brevity, described inthe context of a single embodiment, may also be provided separately orin any subcombination. In addition, references in the singular may alsoinclude the plural (for example, “a” and “an” may refer to one, or oneor more) unless the context specifically states otherwise.

Applicants specifically incorporate the entire content of all citedreferences in this disclosure. Further, when an amount, concentration,or other value or parameter is given as either a range, preferred range,or a list of upper preferable values and lower preferable values, thisis to be understood as specifically disclosing all ranges formed fromany pair of any upper range limit or preferred value and any lower rangelimit or preferred value, regardless of whether ranges are separatelydisclosed. Where a range of numerical values is recited herein, unlessotherwise stated, the range is intended to include the endpointsthereof, and all integers and fractions within the range. It is notintended that the scope of the disclosure be limited to the specificvalues recited when defining a range. It is to be appreciated thatcertain features of the disclosure which are, for clarity, describedabove and below in the context of separate embodiments, may also beprovided separately or in any subcombination.

In one embodiment, the disclosure herein can be construed as excludingany element or process step that does not materially affect the basicand novel characteristics of the composition or process. Additionally,the disclosure can be construed as excluding any element or process stepnot specified herein.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 is a plot of optical density vs. smear resistance for the inks ofthe examples. The filled boxes are the optical density (OD) measurementsand the triangles are smear resistance ratings.

DETAILED DESCRIPTION OF THE DISCLOSURE

Fixer inks are used in combination with aqueous colorant containing inkjet inks to give images that have enhanced coloristic and durabilityproperties and, in particular, smear resistance.

Fixer Ink:

The fixer ink comprises a mixture of a multivalent metal salt and a saltstable, water soluble, predominantly non-ionic, polymeric binder. Thefixer ink may be jetted under and/or over a colored ink. Generally afixer for pigment based inks is designed to increase chroma and/oroptical density. However, fixer inks may also have other additionalunspecified beneficial effects.

Fixer inks typically further comprises an aqueous vehicle. Fixer inkscan also comprise additives such as one or more surfactants or biocidesor mixtures thereof. To minimize the liquid load on the substrate, thefixer ink(s) are typically formulated to be effective at volumes equalto or less than the volume of colored ink being fixed. Typically,although not necessarily, the drop volume of the fixer ink(s) will bethe same as the colored ink(s) and thus, typically, there will be nomore than about one drop of fixer ink for each drop of colored ink.Fixer inks are generally also substantially colorless and do notperceptibly or substantially change the hue of a colored ink beingfixed.

Fixing Agents

Fixing agents are most commonly designed to operate by electrostaticinteraction with the colorant. Thus, an anionic dye or pigmentdispersion is treated with a cationic fixing agent, or a cationiccolorant is treated with anionic fixing agent, thereby immobilizing or“fixing” the colorant. This process is sometimes referred to in the artas “insolubilizing”, “precipitating” or “crashing” the colorant.

The metal in the multivalent metal salt is selected from the groupconsisting of divalent metal ions and trivalent metal ions, and mixturesthereof. Divalent metal ions are selected from the group consisting ofGa²⁺, Cu²⁺, Ni²⁺, Mg²⁺, Zn²⁺ and Ba²⁺ and trivalent metal ions areselected from the group consisting of Al³⁺, Fe³⁺ and Cr³⁺. Typically,the multivalent metal is a divalent metal ion selected from the groupconsisting of Ca²⁺ and Mg²⁺ or a trivalent metal ion such as Al³⁺. Themultivalent metal salt is present in the amount of about 0.5% to about15%, more typically about 1% to about 8%, based on the total weight ofthe fixer ink. The multivalent metal ion can be incorporated into fixerink by addition in a salt form. The associated anionic material can bechosen from any common anionic material, especially halides such aschloride, bromide, iodide and fluoride, nitrates and sulfates. Theanionic form is chosen so that the multivalent cation is soluble in theaqueous solution. The multivalent cationic salts can be used in theirhydrated form. One or more multivalent cationic salts may be used in thepretreatment solution.

For calcium ion, the preferred multivalent cation salts are calciumchloride, calcium nitrate, calcium nitrate hydrate and mixtures thereof.

Non-Ionic Polymeric Binder

The salt stable, water soluble, predominantly non-ionic, polymericbinder is selected from the group consisting of a polyurethanecomprising an ethylene oxide unit, and a methoxylated carboxylatedpolyallylamine; wherein the polymeric binder is substantiallynon-reactive with the colorant. Typically the polyurethane comprising anethylene oxide unit is water soluble, and predominantly non-ionic, andmay have an average number molecular weight of between about 5000 toabout 25,000, more typically about 7,000 to about 20,000.

Examples of suitable water soluble polyurethanes are those in which thepolymer is predominantly stabilized through one or more incorporatedethylene oxide units which provide nonionic functionality. Suitablepolyurethanes are typically prepared by multi-step synthetic processes.In the first stage of prepolymer formation, a diisocyanate is reactedwith a compound, polymer, or mixtures of compounds, mixture of polymersor a mixture thereof, each containing two NCO-reactive groups. Thisintermediate polymer or pre-polymer can be terminated with either anNCO-group or a NCO-reactive group. The terminal groups are defined bythe molar ratio of NCO to NCO-reactive groups in the prepolymer stage.Typically, the pre-polymer is an NCO-terminated material that isachieved by using a molar excess of NCO. Thus, the molar ratio ofdiisocyanate to compounds containing two isocyanate-reactive groups isabout 1.05:1.0 to about 5.0:1.0, typically about 1.10:1.0 to about2.0:1.0. In general compounds containing NCO-reactive groups arehydrophilic compounds with OH groups including non-ionic and anioinic orcationic segments and polyols with OH groups.

Suitable diisocyanates are those that contain either aromatic,cycloaliphatic or aliphatic groups bound to the isocyanate groups.Mixtures of these compounds may also be used. The preferred is aprepolymer that has isocyanates bound to a cycloaliphatic or aliphaticmoieties. If aromatic diisocyanates are used, cycloaliphatic oraliphatic isocyanates are typically present as well.

Examples of suitable diisocyanates include cyclohexane-1,3- and-1,4-diisocyanate;1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophoronediisocyanate or IPDI); bis-(4-isocyanatocyclohexyl)-methane; 1,3- and1,4-bis-(isocyanatomethyl)-cyclohexane; 1-isocyanato-2-isocyanatomethylcyclopentane; 2,4′-diisocyanato-dicyclohexyl methane;bis-(4-isocyanato-3-methyl-cyclohexyl)-methane,alpha,alpha,alpha′,alpha′-tetramethyl-1,3- and/or -1,4-xylylenediisocyanate; 1-isocyanato-1-methyl-4(3)-isocyanatomethyl cyclohexane;and 2,4- and/or 2,6-hexahydrotoluoylene diisocyanate.

Examples of hydrophilic NCO reactive compounds include a compoundcontaining NCO reactive groups, for example, OH groups and a non-ionicdispersing segment, such as an ethylene oxide or ethylene oxidederivative, e.g., —((CH₂)₂O)_(m)—, wherein m can be from about 1 toabout 400, typically from about 5 to about 200. One such example isTegomer® D3403, a polyether diol with polyethylene glycol pendant chainfrom Evonik Industries (Essen, Germany).

Suitable polyols containing at least two NCO reactive groups, which maybe reacted to prepare the prepolymer, are those having a molecularweight of about 60 to about 6000. Of these, the polymeric polyols arebest defined by the number average molecular weight, and can range fromabout 200 to about 6000, typically about 800 to about 3000, and moretypically about 1000 to about 2500. The molecular weights are determinedby hydroxyl group analysis (OH number). Examples of these high molecularweight compounds include polyester, polyether, polycarbonates,polyacetals, poly(meth)acrylates, polyester amides, polythioethers ormixed polymers such as a polyester-polycarbonate where both ester andcarbonate linkages are found in the same polymer. A combination of thesepolymers can also be used. For examples, a polyester polyol and apoly(meth)acrylate polyol may be used in the same polyurethanesynthesis.

Similar NCO reactive materials can be used as described for hydroxycontaining compounds and polymers, but which contain other NCO reactivegroups. Examples would be dithiols, diamines, thioamines and evenhydroxythiols and hydroxylamines. These can either be compounds orpolymers with the molecular weights or number average molecular weightsas described for the polyols.

Suitable polyether polyols are obtained in a known manner by thereaction of starting compounds that contain reactive hydrogen atoms withalkylene oxides such as ethylene oxide, propylene oxide, butylene oxide,styrene oxide, tetrahydrofuran, epichlorohydrin or mixtures of these.Suitable starting compounds containing reactive hydrogen atoms includethe polyhydric alcohols for preparing polyester polyols and, inaddition, water, methanol, ethanol, 1,2,6-hexane triol, 1,2,4-butanetriol, trimethylol ethane, pentaerythritol, mannitol, sorbitol, methylglycoside, sucrose, phenol, isononyl phenol, resorcinol, hydroquinone,1,1,1- and 1,1,2-tris-(hydroxylphenyl)-ethane, dimethylolpropionic acidor dimethylolbutanoic acid. One suitable polyether polyol is Terathane®1400, a 1400 molecular weight a polytetramethylene oxide polyol fromInvista (Wichita, Kans.).

The high molecular weight polyols are generally present in thepolyurethanes in an amount of at least about 5%, typically at leastabout 10% by weight, based on the weight of the polyurethane. Themaximum amount of these polyols is generally about 65%, and typicallyabout 55% by weight, based on the weight of the polyurethane.

In addition to the above-mentioned components, which are typicallydifunctional in the isocyanate polyaddition reaction, mono-functionaland even small portions of trifunctional and higher functionalcomponents generally known in polyurethane chemistry, such astrimethylolpropane or 4-isocyanantomethyl-1,8-octamethylenediisocyanate, may be used in cases in which branching of the NCOprepolymer or polyurethane is desired. However, the NCO prepolymersshould be substantially linear and this may be achieved by maintainingthe average functionality of the prepolymer starting components at orbelow about 2.1, typically between about 1.7 to about 2.

As discussed before, the polyurethanes are typical prepared by chainteminating or extending these NCO containing prepolymers. A suitablemethod of chain extension is to add polyamine to the NCO-prepolymerbefore, during or after the pre-polymer inversion into water.Optionally, the chain extension can occur after pre-polymer inversion.The polyamines include 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane(isophorone diamine or IPDA), bis-(4-amino-cyclohexyl)-methane,bis-(4-amino-3-methylcyclohexyl)-methane, 1,6-diaminohexane, hydrazine,ethylene diamine, diethylene triamine, triethylene tetramine,tetraethylene pentamine and pentaethylene hexamine.

In some cases, chain termination is desirable. Chain terminationrequires the addition, in most cases, of a mono-NCO reactive materialsuch as a monoamine or mono-alcohol.

The materials can be added before, during or after inversion of theprepolymer. Poly-NCO reactive materials can be used where one of theNCO-reactive groups reacts substantially faster than the others. Someexamples would be ethanol amine and diethanol amine. The amine groupwill react much faster with the NCO group than the alcohol.

Suitable chain terminators would be amines or alcohols having an averagefunctionality per molecule of 1, i.e., the number of primary orsecondary amine nitrogens or alcohol oxygens would average 1 permolecule. The desired functionalities can be obtained by using primaryor secondary amino groups. The amines or alcohols are generallyaromatic, aliphatic or alicyclic and contain between 1 to about 30,typically about 2 to about 15 and more typically about 2 to about 10carbon atoms. These may contain additional substituents provided thatthey are not as reactive with isocyanate groups as the amine or alcoholgroups. One suitable example is bis(2-methoxy ethyl)amine (BMEA).

Chain terminators and chain extenders can be used together, either asmixtures or as sequential additions to the NCO-prepolymer.

The amount of chain extender and/or chain terminator to be used inaccordance with the present invention may be dependent upon the numberof isocyanate groups in the prepolymer. Typically, the ratio ofisocyanate groups of the prepolymer to isocyanate-reactive groups of thechain extender/terminator is between about 1.0 to about 0.6 and about1.0 about 1.1, more typically between about 1.0 to about 0.7 and about1.0 to about 1.1, on an equivalent basis. Any isocyanate groups that arenot chain extended/terminated with an amine or alcohol will react withwater, which functions as a chain extender.

The final product is a stable aqueous solution of polyurethane having asolids content of up to about 60% by weight, typically about 15 to about60% by weight and most typically about 30 to about 40% by weight, basedon the total dry polymer over the weight of the total aqueous solution.However, it is always possible to dilute the solution to any minimumsolids content desired.

The nonionic polyurethane may also have ionic components incorporatedinto the polymer. In the case of anionic group substitution, the groupscan be carboxylic acid groups, carboxylate groups, sulphonic acidgroups, sulphonate groups, phosphoric acid groups and phosphonategroups, The acid salts are formed by neutralizing the corresponding acidgroups either prior to, during or after formation of the NCO prepolymer,typically after formation of the NCO prepolymer.

Examples of carboxylic group-containing compounds are thehydroxy-carboxylic acids corresponding to the formula(HO)_(x)Q(COOH)_(y) wherein Q represents a straight or branchedhydrocarbon radical containing 1 to about 12 carbon atoms, x is 1 or 2(typically 2), and y is 1 to 3 (typically 1 or 2).

Examples of these hydroxy-carboxylic acids include citric acid, tartaricacid and hydroxypivalic acid.

Especially preferred acids are those of the above-mentioned formulawherein x=2 and y=1. These dihydroxy alkanoic acids are described inU.S. Pat. No. 3,412,054, the disclosure of which is incorporated byreference herein for all purposes as if fully set forth. Especiallypreferred dihydroxy alkanoic acids are the alpha,alpha-dimethylolalkanoic acids represented by the structural formula:

wherein Q′ is hydrogen or an alkyl group containing 1 to about 8 carbonatoms. The most preferred compound is alpha,alpha-dimethylol propionicacid, i.e., wherein Q′ is methyl in the above formula.

Suitable neutralizing agents for converting the acid groups to saltgroups include tertiary amines, alkali metal cations and ammonia.Preferred neutralizing agents are potassium hydroxide and sodiumhydroxide.

There may be limits to the amount of ionic component in the nonionicpolyurethane, since the ionic component may complex with the multivalentcationic and form a complex that will lead to instability of thenonionic polymer/multivalent cationic solution. The non-ionic componentshould be the dominant component so that addition of polymer tomultivalent cationic solution can lead to a stable solution. A screeningtest for whether a nonionic polymer is stable in the presence of themultivalent cationic salt solution is to mix about 10 wt % polymer andabout 15 wt % of calcium nitrate tetrahydrate and observe whether thesolution is stable. The stability observations may be performed atambient temperature (˜25)° and at 10 minutes and 24 hours.

The methoxylated carboxylated polyallylamine may have the chemicalstructure shown below. Typically, the number average molecular weight isabout 5000 to about 25,000, more typically about 15,000.

wherein n is about 50 to about 200, more typically about 100 to about120. These methoxylated carboxylated polyallylamine are commerciallyavailable as PAA-U5000 from Nitto Boseki Co., Tokyo, Japan. The processfor making the methoxylated carboxylated polyallyamine is known and isdescribed in JP2005089488 entitled “Modified Polyallylamine with GoodCleanability and Printability and Their Manufacture” which isincorporated herein by reference for this purpose. The process caninclude reacting N-alkyldiallylamine-allylamine copolymers with dialkylcarbonates.

Typically, the water soluble predominantly non-ionic polymeric binder isadded to the multivalent cationic salt solution and thispolymer/multivalent cationic salt solution must be stable as a solution.If the nonionic polymer gels, or preciptates in the presence of themultivalent cationic salt solution, as described in the screening testabove, then it cannot be used as a polymer additive for the fixersolution.

The salt stable, water soluble, predominantly non-ionic, polymericbinder is present in the amount of about 0.5% to about 10%, moretypically about 1% to about 5%, based on the total weight of the fixerink.

Ink Jet Ink Composition

Aqueous ink jet inks comprise a colorant, and an aqueous vehicle. Thecolorant may be a dye or a pigment dispersion. Dyes include dispersedyes, reactive dyes, acid dyes and the like. Typically, the pigmentdispersion is an ionically stabilized pigment dispersion.

Aqueous Vehicle:

The aqueous vehicle is water or a mixture of water and at least onewater-miscible organic solvent. Selection of a suitable mixture dependson requirements of the specific application, such as desired surfacetension and viscosity, the selected pigment, drying time of thepigmented ink jet ink, and the type of paper onto which the ink will beprinted. Representative examples of water-soluble organic solvents thatmay be selected include (1) alcohols, such as methyl alcohol, ethylalcohol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol,sec-butyl alcohol, t-butyl alcohol, iso-butyl alcohol, furfuryl alcohol,and tetrahydrofurfuryl alcohol; (2) ketones or ketoalcohols such asacetone, methyl ethyl ketone and diacetone alcohol; (3) ethers, such astetrahydrofuran and dioxane; (4) esters, such as ethyl acetate, ethyllactate, ethylene carbonate and propylene carbonate; (5) polyhydricalcohols, such as ethylene glycol, diethylene glycol, triethyleneglycol, propylene glycol, tetraethylene glycol, polyethylene glycol,glycerol, 2-methyl-2,4-pentanediol 1,2,6-hexanetriol and thiodiglycol;(6) lower alkyl mono- or di-ethers derived from alkylene glycols, suchas ethylene glycol mono-methyl (or -ethyl)ether, diethylene glycolmono-methyl (or -ethyl)ether, propylene glycol mono-methyl (or -ethyl)ether, triethylene glycol mono-methyl (or -ethyl)ether and diethyleneglycol dimethyl (or -ethyl)ether; (7) nitrogen containing cycliccompounds, such as pyrrolidone, N-methyl-2-pyrrolidone, and1,3-dimethyl-2-imidazolidinone; and (8) sulfur-containing compounds suchas dimethyl sulfoxide and tetramethylene sulfone.

The amount of aqueous carrier medium in the ink is typically in therange of about 70% to about 99.8%, and typically about 80% to about99.8%, based on total weight of the ink.

The aqueous carrier medium can be made to be fast penetrating (rapiddrying) by including penetrating agents such as glycol ethers and1,2-alkanediols. Glycol ethers include ethylene glycol monobutyl ether,diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propylether, diethylene glycol mono-iso-propyl ether, ethylene glycolmono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethyleneglycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether,diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol,propylene glycol mono-t-butyl ether, propylene glycol mono-n-propylether, propylene glycol mono-iso-propyl ether, propylene glycolmono-n-butyl ether, dipropylene glycol mono-n-butyl ether, dipropyleneglycol mono-n-propyl ether, and dipropylene glycol monoisopropyl ether.1,2-Alkanediols are typically 1,2-C4-6 alkanediols, most typically1,2-hexanediol.

The amount of glycol ether(s) and 1,2-alkanediol(s) added must beproperly determined, but is typically in the range of from about 1 toabout 15% by weight and more typically about 2 to about 10% by weight,based on the total weight of the ink.

An aqueous vehicle will typically contain about 30% to about 95% waterwith the balance (i.e., about 70% to about 5%) being the water-solublesolvent. Fixer ink compositions typically contain about 60% to about 95%water, based on the total weight of the aqueous vehicle.

Other Ingredients

Other ingredients (additives) can be formulated into the fixer ink, tothe extent that such other ingredients do not interfere with thestability and jettability of the finished ink, which may be readilydetermined by routine experimentation. Such other ingredients are in ageneral sense well known in the art.

Commonly, surfactants are added to the ink to adjust surface tension andwetting properties. Examples of suitable non-ionic surfactants includeethoxylated acetylene diols (e.g. Surfynols® series from Air Products),ethoxylated primary (e.g. Neodol® series from Shell and Tomadol® seriesfrom Tomah Products) and secondary (e.g. Tergitol® series from DowChemical) alcohols, Surfactants are typically used in the amount ofabout 0.01 to about 5% and typically about 0.2 to about 2%, based on thetotal weight of the ink.

Suitable cationic surfactants include, for example, quaternized ammoniumor pyridinium surfactants, such as dodecyltrimethylammonium chloride,cetyltrimethylammonium bromide, cetyltrimethylpyridinium chloride andothers.

Amphoteric surfactants that, within a certain pH range, are cationic mayalso be used. In this case the pH of the liquid composition must beadjusted below the isoelectric point of the surfactant. Some examples ofuseful zwitterionic surfactants include N,N-dimethyl-N-tetradecyl amineoxide (NTAO), N,N-dimethyl N-hexadecyl amine oxide (NHAO) and relatedamine oxide compounds. Another example is N-dodecyl-N,N-dimethylglycine. Yet other examples include phosphates, phosphites,phosphonates, lecithins and the like, and phosphonate esters such asphosphomyelin.

Biocides may be used to inhibit growth of microorganisms. One suitableexample is Proxel® GXL from Avecia, Machester, UK.

The components described above can be combined to make a fixer ink invarious proportions and combinations in order to achieve desired inkproperties, as generally described above, and as generally recognized bythose of ordinary skill in the art. Some experimentation may benecessary to optimize inks for a particular end use, but suchoptimization is generally within the ordinary skill in the art.

The fixer ink has physical properties adjusted to the ejectingconditions and printhead design. Drop velocity, separation length of thedroplets, drop size and stream stability are greatly affected by thesurface tension and the viscosity of the ink. Fixer inks typically havea surface tension in the range of about 20 dyne/cm to about 70 dyne/cmat 25° C. Viscosity can be as high as 30 cP at 25° C., but is typicallysomewhat lower. The fixer ink of this disclosure can be particularlyadvantageous for applications where low viscosity is required. Thus theviscosity (at 25° C.) of the inks can be less than about 7 cps, or lessthan about 5 cps, and even less than about 3 but typically no less thanabout 1 cps. The inks should have excellent storage stability for longperiods so as not clog to a significant extent in an ink jet apparatus.Further, the ink should not corrode parts of the ink jet printing deviceit comes in contact with, and it should be essentially odorless andnon-toxic.

Colorant:

The colorant may be a pigment dispersion, self dispersed pigment or adye. The pigment dispersion comprises a pigment and a dispersant, moretypically and ionically stabilized dispersant.

Suitable pigments are those generally well-known in the art for aqueousinkjet inks. Traditionally, pigments are stabilized by dispersingagents, such as polymeric dispersants or surfactants, to produce astable dispersion of the pigment in the vehicle. More recently though,so-called “self-dispersible” or “selfdispersing” pigments (hereafter“SDP”) have been developed. As the name would imply, SDPs aredispersible in water without dispersants. Dispersed dyes are alsoconsidered pigments as they are insoluble in the aqueous inks usedherein.

The dispersant or surface treatment applied to the pigment creates ananionic surface charge (“anionic pigment dispersion”). Typically, thatsurface charge is imparted predominately by ionizable carboxylic acid(carboxylate) groups.

The dispersant used to stabilize the pigment is typically a polymericdispersant. Either structured or random polymers may be used, althoughstructured polymers are preferred for use as dispersants for reasonswell known in the art. The term “structured polymer” means polymershaving a block, branched or graft structure. Examples of structuredpolymers include AB or BAB block copolymers such as disclosed in U.S.Pat. No. 5,085,698; ABC block copolymers such as disclosed inEP-A-0556649; and graft polymers such as disclosed in U.S. Pat. No.5,231,131. Other polymeric dispersants that can be used are described,for example, in U.S. Pat. No. 6,117,921, U.S. Pat. No. 6,262,152, U.S.Pat. No. 6,306,994 and U.S. Pat. No. 6,433,117. The disclosure of eachof these publications is incorporated herein by reference for allpurposes as if fully set forth. Polymer dispersants suitable for use inthe present invention comprise both hydrophobic and hydrophilicmonomers. Some examples of hydrophobic monomers used in random polymersare methyl methacrylate, n-butyl methacrylate, 2-ethylhexylmethacrylate, benzyl methacrylate, 2-phenylethyl methacrylate and thecorresponding acrylates. Examples of hydrophilic monomers aremethacrylic acid, acrylic acid, dimethylaminoethyl(meth)acrylate andsalts thereof. Also quaternary salts of dimethylaminoethyl(meth)acrylatemay be employed.

The pigment dispersions, wherein pigments are stabilized by addition ofdispersing agents, may be prepared by methods known in the art. It isgenerally desirable to make the stabilized pigment in a concentratedform, which is subsequently diluted with a suitable liquid containingthe desired additives. The pigment dispersion is first prepared bypremixing the selected pigment(s), polymeric dispersant(s), aneutralizing agent specifically to ionize the carboxylic acid groupcontained in polymeric dispersant including alkaline bases (such aspotassium hydroxide), or tertiary amines (such as dimethylethanol amine)in an aqueous carrier medium (such as water and, optionally, awater-miscible solvent, for example, triethylene glycol monobutylether), and then dispersing or deflocculating the pigment. Thedispersing step may be accomplished in a 2-roll mill, media mill, ahorizontal mini mill, a ball mill, an attritor, or by passing themixture through a plurality of nozzles within a liquid jet interactionchamber at a liquid pressure of at least about 5,000 psi up to about50,000 psi, typically about 15,000 to about 25,000 psi to produce auniform dispersion of the pigment particles in the aqueous carriermedium (microfluidizer). Alternatively, the concentrates may be preparedby dry milling the polymeric dispersant and the pigment under pressure.The media for the media mill is chosen from commonly available media,including zirconia, YTZ, and nylon. These various dispersion processesare in a general sense well-known in the art, as exemplified by, U.S.Pat. No. 5,022,592, U.S. Pat. No. 5,026,427, U.S. Pat. No. 5,310,778,U.S. Pat. No. 5,891,231, U.S. Pat. No. 5,679,138, U.S. Pat. No.5,976,232 and US20030089277. All of these documents are incorporated byreference herein for all purposes as if fully set forth. Preferred are2-roll mill, media mill, and by passing the mixture through a pluralityof nozzles within a liquid jet interaction chamber at a liquid pressureof at least about 5,000 psi upto about 50,000 psi, typically about15,000 to about 25,000 psi.

After the milling process is complete the pigment concentrate may be“let down” into an aqueous system. “Let down” refers to the dilution ofthe concentrate with mixing or dispersing, the intensity of themixing/dispersing normally being determined by trial and error usingroutine methodology, and often being dependent on the combination of thepolymeric dispersant, solvent and pigment. The determination ofsufficient let down conditions is needed for all combinations of thepolymeric dispersant, the solvent and the pigment.

After the dispersion preparation, the amount of water-miscible solventmay be more than some ink jet applications will tolerate. For some ofthe dispersions, it thus may be necessary to ultrafilter the finaldispersion to reduce the amount of water-miscible solvent. To improvestability and reduce the viscosity of the pigment dispersion, it may beheat treated by heating from about 30° C. to about 100° C., with thepreferred temperature being about 70° C. for about 10 to about 24 hours.Longer heating does not affect the performance of the dispersion.

The amount of polymeric dispersants required to stabilize the pigment isdependent upon the specific polymeric dispersants, the pigment andvehicle interaction. The weight ratio of pigment to polymericdispersants will typically range from about 0.5 to about 6. A preferredrange is about 0.75 to about 4.

More recently though, so-called “self-dispersible” or “self-dispersing”pigments (hereafter “SDP”) have been developed. As the name would imply,SDPs are dispersible in water, or vehicle, without dispersants. See, forexample, U.S. Pat. No. 5,554,739, U.S. Pat. No. 5,571,311, U.S. Pat. No.5,609,671, U.S. Pat. No. 5,672,198, U.S. Pat. No. 5,698,016, U.S. Pat.No. 5,707,432, U.S. Pat. No. 5,718,746, U.S. Pat. No. 5,747,562, U.S.Pat. No. 5,749,950, U.S. Pat. No. 5,803,959, U.S. Pat. No. 5,837,045,U.S. Pat. No. 5,846,307, U.S. Pat. No. 5,851,280, U.S. Pat. No.5,861,447, U.S. Pat. No. 5,885,335, U.S. Pat. No. 5,895,522, U.S. Pat.No. 5,922,118, U.S. Pat. No. 5,928,419, U.S. Pat. No. 5,976,233, U.S.Pat. No. 6,057,384, U.S. Pat. No. 6,099,632, U.S. Pat. No. 6,123,759,U.S. Pat. No. 6,153,001, U.S. Pat. No. 6,221,141, U.S. Pat. No.6,221,142, U.S. Pat. No. 6,221,143, U.S. Pat. No. 6,277,183, U.S. Pat.No. 6,281,267, U.S. Pat. No. 6,329,446, U.S. Pat. No. 6,332,919, U.S.Pat. No. 6,375,317, US2001/0035110, EP-A-1086997, EP-A-1114851,EP-A-1158030, EP-A-1167471, EP-A-1122286, WO01/10963, WO01/25340 andWO01/94476, the disclosures of which are incorporated by referenceherein for all purposes as if fully set forth.

A pigment may be stabilized to dispersion by surface treatment to beself-dispersing (see, for example, previously incorporated WO 01/94476),by treatment with dispersant in the traditional way, or by somecombination of surface treatment and dispersant.

Examples of quaternary self-dispersed pigments include those withpendant quaternized amine groups. The preparation of such pigments isdescribed in U.S. Pat. No. 5,851,280 and U.S. Pat. No. 6,221,143 (thedisclosures of which are incorporated by reference herein for allpurposes as if fully set forth).

Representative commercial pigments in dry form include the following:

COLOR INDEX (CI) TRADE NAME MANUFACTURER PIGMENT NAME PERMANENT YELLOWDHG HOECHST YELLOW 12 PERMANENT YELLOW GR HOECHST YELLOW 13 PERMANENTYELLOW G HOECHST YELLOW 14 PERMANENT YELLOW NCG-71 HOECHST YELLOW 16PERMANENT YELLOW NCG-71 HOECHST YELLOW 16 PERMANENT YELLOW GG HOECHSTYELLOW 17 HANSA YELLOW RA HOECHST YELLOW 73 HANSA BRILLIANT YELLOW5GX-02 HOECHST YELLOW 74 DALAMAR ® YELLOW YT-858-D HEUBACH YELLOW 74HANSA YELLOW X HOECHST YELLOW 75 NOVOPERM ® YELLOW HR HOECHST YELLOW 83CHROMOPHTAL ® YELLOW 3G CIBA-GEIGY YELLOW 93 CHROMOPHTAL ® YELLOW GRCIBA-GEIGY YELLOW 95 NOVOPERM ® YELLOW FGL HOECHST YELLOW 97 HANSABRILLIANT YELLOW 10GX HOECHST YELLOW 98 PERMANENT YELLOW G3R-01 HOECHSTYELLOW 114 CHROMOPHTAL ® YELLOW 8G CIBA-GEIGY YELLOW 128 IRGAZIN ®YELLOW 5GT CIBA-GEIGY YELLOW 129 HOSTAPERM ® YELLOW H4G HOECHST YELLOW151 HOSTAPERM ® YELLOW H3G HOECHST YELLOW 154 L74-1357 YELLOW SUN CHEML75-1331 YELLOW. SUN CHEM L75-2377 YELLOW SUN CHEM. HOSTAPERM ® ORANGEGR HOECHST ORANGE 43 PALIOGEN ® ORANGE BASF ORANGE 51 IRGALITE ® RUBINE4BL CIBA-GEIGY RED 57:1 QUINDO ® MAGENTA MOBAY RED 122 INDOFAST ®BRILLIANT SCARLET MOBAY RED 123 HOSTAPERM .RTM. SCARLET GO HOECHST RED168 PERMANENT RUBINE F6B HOECHST RED 184 MONASTRAL ® MAGENTA CIBA-GEIGYRED 202 HELIOGEN .RTM. BLUE L 6901F BASF BLUE 15:2 HELIOGEN ® BLUE NBD7010 BASF HELIOGEN ® BLUE K 7090 BASF BLUE 15:3 HELIOGEN ® BLUE L 7101FBASF BLUE 15:4 PALIOGEN ® BLUE L 6470 BASF BLUE 60 HEUCOPHTHAL ® BLUE G,XBT-583D HEUBACH BLUE 15:3 HELIOGEN ® GREEN K 8683 BASF GREEN 7HELIOGEN ® GREEN L 9140 BASF GREEN 36 MONASTRAL ® VIOLET R CIBA-GEIGYVIOLET 19 MONASTRAL ® RED B CIBA-GEIGY VIOLET 19 QUINDO ® RED R6700MOBAY QUINDO ® RED R6713 MOBAY INDOFAST ® VIOLET MOBAY VIOLET 23MONASTRAL ®. VIOLET MAROON B CIBA-GEIGY VIOLET 42 SPECIAL BLACK 4ADEGUSSA BLACK 7 STERLING ® NS 76 BLACK CABOT BLACK 7 STERLING ® NSX 76CABOT BLACK 7 MOGUL L CABOT BLACK 7

Representative commercial pigments available in the form of a water-wetpresscake include: Heucophthal® Blue BT-585-P, Toluidine Red Y (C.I.Pigment Red 3), Quindo® Magenta (Pigment Red 122), Magenta RV-6831presscake (Mobay Chemical, Harmon Division, Haledon, N.J.), Sunfast®Magenta 122 (Sun Chemical Corp., Cincinnati, Ohio), Indo® BrilliantScarlet (Pigment Red 123, C.I. No. 71145), Toluidine Red B (C.I. PigmentRed 3), Watchung® Red B (C.I. Pigment Red 48), Permanent RubineF6B13-1731 (Pigment Red 184), Hansa® Yellow (Pigment Yellow 98),Dalamar® Yellow YT-839-P (Pigment Yellow 74, C.I. No. 11741, Sunbrite®Yellow 17 (Sun Chemical Corp, Cincinnati, Ohio), Toluidine Yellow G(C.I. Pigment Yellow 1), Pigment Scarlet (CI Pigment Red 60), AuricBrown (CI Pigment Brown 6), etc. Black pigments, such as carbon black,generally are not available in the form of aqueous presscakes.

Cationic dyes typically have a structural skeleton of cyanine, azo,azomethine, xanthene, triphenylmethane, methine, polymethine,phthalocyanine, or the like. Cationic dyes include C.I. Basic Yellow 1,C.I. Basic Yellow 11, C. I. Basic Yellow 13, C.I. Basic Yellow 19, C.I.Basic Yellow 21, C.I. Basic Yellow 25, C.I. Basic Yellow 33, C.I. BasicYellow 36, C.I. Basic Red 1, C.I. Basic Red 2, C.I. Basic Red 9, C.I.Basic Red 12, C.I. Basic Red 13, C.I. Basic Red 38, C.I. Basic Red 39,C.I. Basic Red 92, C.I. Basic Blue 1, C.I. Basic Blue 3, C.I. Basic Blue5, C.I. Basic Blue 9, C. I. Basic Blue 19, C.I. Basic Blue 24, C.I.Basic Blue 25, C.I. Basic Blue 26, C.I. Basic Blue 28, C.I. Basic Blue45, C.I. Basic Blue 54, and C.I. Basic Blue 65. These dyes may be usedin combination for preparation of a black ink.

Anionic dyes include Acid Yellow 11, Acid Yellow 17, Acid Yellow 23,Acid Yellow 25, Acid Yellow 29, Acid Yellow 42, Acid Yellow 49, AcidYellow 61, Acid Yellow 71, Direct Yellow 12, Direct Yellow 24, DirectYellow 26, Direct Yellow 44, Direct Yellow 86, Direct Yellow 87, DirectYellow 98, Direct Yellow 100, Direct Yellow 130, Direct Yellow 86,Direct Yellow 132, Direct Yellow 142, Acid Red 1, Acid Red 6, Acid Red8, Acid Red 32, Acid Red 35, Acid Red 37, Acid Red 51, Acid Red 52, AcidRed 80, Acid Red 85, Acid Red 87, Acid Red 92, Acid Red 94, Acid Red115, Acid Red 180, Acid Red 254, Acid Red 256, Acid Red 289, Acid Red315, Acid Red 317, Direct Red 1, Direct Red 4, Direct Red 13, Direct Red17, Direct Red 23, Direct Red 28, Direct Red 31, Direct Red 62, DirectRed 79, Direct Red 81, Direct Red 83, Direct Red 89, Direct Red 227,Direct Red 240, Direct Red 242, Direct Red 243, Acid Blue 9, Acid Blue22, Acid Blue 40, Acid Blue 59, Acid Blue 93, Acid Blue 102, Acid Blue104, Acid Blue 113, Acid Blue 117, Acid Blue 120, Acid Blue 167, AcidBlue 229, Acid Blue 234, Acid Blue 254, Direct Blue 6, Direct Blue 22,Direct Blue 25, Direct Blue 71, Direct Blue 78, Direct Blue 86, DirectBlue 90, Direct Blue 106, Direct Blue 199.

The black colorant may also be a dye as, for example, the black dyedisclosed in U.S. Pat. No. 5,753,016, the disclosure of which is hereinincorporated by reference. The black colorant may also be a combinationof dye and pigment as, for example, disclosed in previously incorporatedU.S. Pat. No. 6,277,184.

Other Ingredients:

Other ingredients may be formulated into the inkjet ink, to the extentthat such other ingredients do not interfere with the stability andjettablity of the ink, which may be readily determined by routineexperimentation. Such other ingredients are in a general sense wellknown in the art.

Commonly, surfactants are added to the ink to adjust surface tension andwetting properties. Suitable surfactants include ethoxylated acetylenediols (e.g. Surfynols® series from Air Products), ethoxylated primary(e.g. Neodol® series from Shell and Tomadol® series from Tomah Products)and secondary (e.g. Tergitol® series from Dow Chemical) alcohols,sulfosuccinates (e.g. Aerosol® series from Cytec), organosilicones (e.g.Silwet® series from GE Silicons) and fluoro surfactants (e.g. Zonyl®series from DuPont). Surfactants are typically used in the amount ofabout 0.01 to about 5% and typically about 0.2 to about 2%, based on thetotal weight of the ink.

Biocides may be used to inhibit growth of microorganisms. One suitableexample is Proxel GXL from Avecia, Machester, UK.

Inclusion of sequestering (or chelating) agents such asethylenediaminetetraacetic acid (EDTA), iminodiacetic acid (IDA),ethylenediamine-di(ohydroxyphenylacetic acid) (EDDHA), nitrilotriaceticacid (NTA), dihydroxyethylglycine (DHEG),trans-1,2-cyclohexanediaminetetraacetic acid (CyDTA),dethylenetriamine-N,N,N′,N″,N″-pentaacetic acid (DTPA), andglycoletherdiamineN,N,N′,N′-tetraacetic acid (GEDTA), and salts thereof,may be advantageous, for example, to eliminate deleterious effects ofheavy metal impurities. The inks can contain compatible polymers otherthan pigment dispersant and co-reactive species. The oligomers orpolymers can be based on acrylic, urethane, polyester, polyamide,polyvinyl, polyether, polyamine and cellulosic structures; the polymeror oligomer structures could include random, block, branched, star ordendrimer structures. They can be soluble, or present as a dispersion,latex or hydrosol. The latex or dispersion particles can have ahomogeneous or core/shell structure.

Ink Properties:

Drop velocity, separation length of the droplets, drop size and streamstability are greatly affected by the surface tension and the viscosityof the ink. Ink jet inks typically have a surface tension in the rangeof about 20 dyne/cm to about 70 dyne/cm at 25° C. Viscosity can be ashigh as 30 cP at 25° C. (30 cP or less), but is typically somewhatlower. The physical properties of the ink are adjusted to the ejectingconditions and print-head design. The inks should have excellent storagestability for long periods so as not clog to a significant extent in anink jet apparatus. Further, the ink should not corrode parts of theinkjet-printing device it comes in contact with, and it should beessentially odorless and non-toxic.

The ink set of this invention can be particularly advantageous forapplications where low viscosity is required. Thus the viscosity (at 25°C.) of the inks can be less than about 7 cps, or less than about 5 cps,and even less than about 3.5 cps.

Proportions of Ingredients:

The components described above and below may be combined to make an inkin various proportions and combinations in order to achieve desired inkproperties, as generally described above, and as generally recognized bythose of ordinary skill in the art. Some experimentation may benecessary to optimize inks for a particular end use, but suchoptimization is generally within the ordinary skill in the art.

For example, the amount of vehicle in an ink, whether aqueous ornonaqueous, is typically in the range of about 70% to about 99.8%, andmore typically about 80% to about 99.8%, based on total weight of theink.

In a colored ink, colorant will generally be present in amounts up toabout 12%, and more typically in the range of about 0.1 to about 9%, byweight of the total ink. Dispersants, when needed for stabilization ofan insoluble colorant, are employed at levels based on the amount ofcolorant and are usually expressed as a weight ratio. Generally,dispersants are employed at a pigment-to-dispersant weight ratio in therange of about 1:3 to about 4:1.

Other ingredients (additives), when present, generally comprise lessthan about 15% by weight, based on the total weight of the ink.surfactants, when added, are generally in the range of about 0.2 toabout 3% by weight based on the total weight of the ink. Polymers otherthan pigment dispersant and co-reactive species can be added as needed,but will generally be less than about 15% by weight based on the totalweight of the ink.

Ink Sets:

The term “ink set” refers to all the individual inks or other fluids,example the fixer ink of this disclosure, an inkjet printer is equippedto jet.

In one typical embodiment, the ink set comprises the fixer ink and atleast two differently colored inkjet inks. More typically ink setscomprise the fixer ink and at least three differently colored inks (suchas CMY), and still more typically the fixer ink and at least fourdifferently colored inks (such as CMYK).

In addition to the CMYK inks mentioned above, the ink sets may containadditional differently colored inks, as well as different strengthversions of the CMYK and other inks.

For example, the inks sets of the present invention can comprisefull-strength versions of one or more of the inks in the ink set, aswell as “light” versions thereof.

Additional colors for the inkjet ink set may include, for example,white, or ange, violet, green, red and/or blue.

In a specific embodiment of the present disclosure, there is provided anink set comprising an ink comprising an anionically stabilized pigmentink and the fixer ink of the disclosure. In another embodiment, an inkset comprises plural, differently colored ionically stabilizeddispersion based pigment inks and a fixer ink.

The disclosure provides a method for printing a substrate, comprising:

(a) providing an in ink set, comprising:

-   -   an aqueous colorant containing ink jet ink;    -   a fixer ink comprising:        -   (i) a multivalent metal salt, wherein the metal is selected            from the group consisting of divalent metal ions such as            Ga²⁺, Cu²⁺, Ni²⁺, Mg²⁺, Zn²⁺ and Ba²⁺, trivalent metal ions,            such as Al³⁺, Fe³⁺ and Cr³⁺, and mixtures thereof; and        -   (ii) a salt stable, water soluble, predominantly non-ionic,            polymeric binder selected from the group consisting of a            polyurethane comprising an ethylene oxide unit, and a            methoxylated carboxylated polyallylamine; wherein the            polymeric binder is substantially non-reactive with the            colorant;

(b) applying the ink jettable fixer ink to the substrate, and

(c) applying the aqueous colorant containing ink jet ink to thesubstrate.

The fixer ink may be jetted under and/or over a colored ink to enhancethe coloristic or durability properties. Generally a fixer for pigmentsis designed to increase chroma and/or optical density. However, fixersmay also have other and/or additional beneficial effects.

The description of illustrative and preferred embodiments of the presentdisclosure is not intended to limit the scope of the disclosure. Variousmodifications, alternative constructions and equivalents may be employedwithout departing from the true spirit and scope of the appended claims.This disclosure now will be further illustrated, but not limited, by thefollowing examples.

The following Examples illustrate certain embodiments of the disclosure.All parts, percentages and proportions are by weight unless otherwiseindicated.

EXAMPLES Ingredients and Abbreviations

DMPA=dimethylol propionic acid

IPDI=isophoronediisocyanate

BMEA=bis(2-methoxy ethyl)amine

Tetraglyme=tetraethylene glycol dimethyl ether

THF=tetrahydrofuran

Unless otherwise noted, the above chemicals were obtained from Aldrich

(Milwaukee, Wis.) or other similar suppliers of laboratory chemicals.Liponic™ EG-1—ethoxylated glycerin humectant from Lipo Chemicals Inc.(Patterson, N.J.)

Surfynol® 465—acetylene glycol nonionic surfactant from Air Products(Allentown, Pa.)

Tergitol 15-S-7—secondary alcohol ethoxylate a nonionic surfactant fromDow Chemical (Midland, Mich.)

Terathane® 1400—a polytetramethylene oxide polyol from Invista (Wichita,Kans.)

Tegomer D3403—Polyether diol from Evonik Industries (Essen, Germany)

PAA-U5000—Methoxycarbonylated polyallylamine from Nitto Boseki Co.(Tokyo, Japan)

Pulset JK-177—Dimethylamine-epichlorohydrin copolymer from Esprixtechnologies (Sarasota, Fla.)

Proxel® GXL 0 20% aqueous dipropylene glycol solution preservative fromAvecia (Manchester, UK).

Polymeric Dispersants:

The following example was based on group transfer polymerization (GTP),although other types of polymerization processes can be used to generatesimilar types of polymer.

Standard laboratory techniques were employed for the following examples.

The acid value was determined by titration and was reported as meq/gramof polymer solids. Molecular weight was determined by GPC. The GPCseparations were carried out using a four column set consisting of two500-A, and two 100-A 30 cm×7.8 mm i.d. Microstyragel columns (Waters,Milford, Mass.). The THF mobile phase was delivered by a Hewlett-Packard(PaloAlto, Calif.) model 1090 gradient liquid chromatograph at aflowrate of 1.0 mL/min. The eluting species were detected using aHewlett-Packard 1047A differential refractive detector. Narrowlow-molecular-weight poly(methylmethacrylate) standards were used ascalibrants. The particle size was determined by dynamic light scatteringusing a Microtrac Analyzer, Largo Fla. For many of the dispersion steps,a Model 100 F or Y, Microfluidics System was used (Newton Mass.)

It should be noted that, in referring to the polymer compositions, adouble slash indicates a separation between blocks and a single slashindicates a random copolymer. Thus, for example, BZMA/MAA 90/10 is arandom copolymer having about 90 wt % benzyl methacrylate (BZMA) andabout 10 wt % methacrylic acid (MAA) units in the final polymer.

Polymer 1a: BZMA/MAA 90/10 Random Linear Copolymer

A 5-liter flask was equipped with a mechanical stirrer, thermometer, N₂inlet, drying tube outlet, and addition funnels. THF, 1715.1 g, wascharged to the flask. The catalyst (tetrabutyl ammoniumm-chlorobenzoate, 1.2 ml of a 1.0 M solution in acetonitrile) was thenadded. Initiator (1-methoxy-1-trimethylsiloxy-2-methyl propene, 51.33 g(0.295 moles)) was injected. Feed I (tetrabutyl ammoniumm-chlorobenzoate, 1.2 ml of a 1.0 M solution in acetonitrile and THF,10.0 g) was started and added over 180 minutes. Feed II (trimethylsilylmethacrylate, 267.6 g (1.69 moles) and benzyl methacrylate (BZMA),1305.6 g (7.42 moles)) was started at 0.0 minutes and added over 70minutes.

At 173 minutes, 60.5 g of methanol were added to the above solution anddistillation begun. During the first stage of distillation, 503.0 g ofmaterial were removed. The final polymer solution was 51.5% solids.

The polymer had a composition of BZMA/MAA 90/10; molecular weight (Mn)of 5048; and an acid value of 1.24 (milliequivalents/gram of polymersolids) based on total solids.

Polymer 1 b: BZMA/MAA 90/10 Random Linear Copolymer with 2-pyrrolidoneas Final Solvent

In a 2 liter flask, 1000 g of Polymer 1a solution were added. Thesolution was heated to reflux and 284 g of solvent were distilled off.Then 221 g of 2-pyrrolidone were added to the flask. After another 156 gof solvent were distilled off, 266 g of 2-pyrrolidone were added to makea polymer solution of 47% solids.

Dispersion Preparation—Black Dispersion (PD1)

An aqueous black pigment dispersion was prepared by mixing the followingingredients with adequate stirring:

INGREDIENT AMOUNT (G) Polymer 1b 268.3 Potassium hydroxide (4.5% solids)239.4 Deionized water 1142 Carbon black (FW-18 Degussa) 330Triethyleneglycol monobutyl ether 220

These ingredients were well mixed and dispersed with a MicrofluidicsSystem to yield a 15 wt % pigment solids dispersion. The dispersion wasthen purified by removing excess solvent, Triethyleneglycol monobutylether, through an ultrafiltration process to yield a 9.86 wt % pigmentsolids dispersion that has less than 1.0 wt % of solvent (other thanwater), and an average particle size of 107 nm.

Inkjet Ink Preparation (Ink A):

An Ink was prepared by mixing the following ingredients with adequatestirring:

INGREDIENT AMOUNT (G) PD1 30.4 1,2-hexanediol 4 Glycerol 10 Ethyleneglycol 5 Liponic ™ EG-1 5 Surfynol ® 465 0.5 Proxel GXL 0.2 Deionizedwater 44.9

This made an ink that contained 3.0 wt % pigment.

Water Soluble Polyurethane with Ethylene Oxide Unit (PU)

To a dry, alkali- and acid-free flask, equipped with an addition funnel,a condenser, stirrer and a nitrogen gas line, was added 130 g Terathane1000, 65 g

Tegomer D3403 and 6 g DMPA to dissolve in 54 g Tetraglyme solvent Thecontents were heated to 70° C. and mixed well. 60 g IPDI were then addedto the flask via the addition funnel over 60 min, with any residual IPDIbeing rinsed from the addition funnel into the flask with 5 gTetraglyme.

The flask temperature was raised to 80° C., then held at 80° C. untilNCO % was less than 1.3%. Then, 11 g BMEA were added over 5 minutes.After 2 hr at 80° C., the polyurethane solution was inverted under highspeed mixing by adding 100 g 2.5% KOH water solution followed by anadditional 450 g water. The polyurethane solution had a viscosity of18.6 cps, 29.6% solids, acid value of 0.17 and 22 wt % of ethylene oxideunit based on polymer solid.

Fixer Ink Preparation:

Fixer inks were prepared by mixing the following ingredients shown inTable 1 with adequate stirring. Weight percentage was based on solidweight of the ingredient.

Fixer 1 (comp 1) contains an organic cationic substance,N-methylmorpholine neutralized by methane sulfonic acid as the fixingagent. Fixer 2 (comp 2) contains calcium nitrate hydrate, which is amultivalent salt, as the fixing agent. Fixer 3 (comp 3) containsPulset®JK-177, a cationic polymer, dimethylamine-epichlorohydrincopolymer from Esprix technologies and calcium nitrate hydrate as thefixing agent

Fixer 4 contains the calcium nitrate hydrate and nonionic polyurethane(PU) as the fixing agent. Fixer 5 contains the calcium nitrate hydrateand non-ionic methoxylated carboxylated polyallylamine (PAA-U5000) asthe fixing agent.

TABLE 1 Fixer Ink Formulation Fixer 2 Fixer 3 Ingredients (%) Fixer 1(Comp 1) (Comp 2) (Comp 3) Fixer 4 Fixer 5 PAA-U5000 2.0 PU 3.5 Pulset ®JK-177 4.0 N-methylmorpholine 3.5 Calcium nitrate hydrate 3.5 2.0 3.53.5 2-Pyrrolidone 4.0 4.0 4.0 4.0 4.0 Tetraethylene glycol 6.0 6.0 6.06.0 6.0 1,5 pentanediol 10.0 10.0 10.0 10.0 10.0 Tergitol ® 15-S-7 1.251.25 1.25 1.25 1.25 Proxel ® GXL 0.2 0.2 0.2 0.2 0.2 Methane SulfonicAcid As needed (to pH 4.5) Water (balance to 100%) Balance BalanceBalance Balance Balance

TABLE 2 Fixer Ink Properties Fixer 1 Fixer 2 Fixer 3 (Comp 1) (Comp 2)(Comp 3) Fixer 4 Fixer 5 Viscosity (cps) 2.48 2.22 2.55 3.10 3.25 pH4.40 7.05 5.20 6.00 9.94 Surface tension 29.7 2.98 29.7 32.3 30.1 (mN/m)

Example 1-5

Ink A with Fixer 1-Fixer 5 were printed under various print conditions.The substrate used in all print tests was Xerox 4200 plain paper.

One pass printing was performed on a printing apparatus consisting oftwo Canon I-960 inkjet printheads mounted in fixed position above arotating drum to which the substrate was attached. The two printheadswere aligned to print on the same area of the substrate and wereapproximately 1 cm wide, producing a printed stripe of the same width.The print condition was set to print the fixer from one printheadimmediately followed by printing of ink from the second head on top ofthe freshly printed (“wet”) fixer. The amount of ink applied wasestimated to be about 17 μg/mm². Different levels of fixer coverage weretested. The amount of fixer applied varied from 20%, 33%, 50% and 100%relative to amount of ink applied which corresponded to about 3.4, 5.7,8.5 and 17 μg/mm². A test with ink only, no fixer (“0% coverage”) wasrepeated as part of each series of tests with different fixer.

Optical densities were measured with a Greytag-Macbeth SpectroEye(Greytag-Macbeth AG, Regensdorf, Switzerland).

Highlighter Smear Resistance Measurement:

To determine smear, a pattern consisting of three 1 cm wide parallelstripes spaced about 7 mm apart were printed. Two strokes from ahighlighter, one on top of the other, were drawn across the five printedlines. Highlighter pen used was Sharpie® Accent® alkaline based. Thistesting was performed one hour after printing the test pattern. Thestripes were inspected from smear-fastness according to the followingordinal scale and the highest applicable ranking applied:

-   -   5=No smear visible    -   4=slight smear, narrow, doesn't run clear to next stripe    -   3=moderate smear, may be full width of highlighter, but light in        color    -   2=noticeable smear, runs full width of area between stripes    -   1=severe smear, considerable color transfer, may be some damage        to stripe    -   0=Ink largely removed from stripe with highlighter

Table 3 summarized OD and smear-fastness results.

TABLE 3 Fixer Ink applied Fixer Ink applied Fixer Ink applied Fixer Inkapplied Fixer Ink applied Fixer (0%) (20%) (30%) (50%) (100%) Fixer 1 OD0.94 1.12 1.25 1.26 1.37 (comp 1) Smear 5.0 4.0 4.0 3.5 3.0 fastnessFixer 2 OD 0.94 1.35 1.48 1.59 1.55 (comp 2) Smear 5.0 3.5 2.5 1.5 2.0fastness Fixer 3 OD 0.94 1.39 1.51 1.55 1.57 (comp 3) Smear 5.0 3.0 2.52.5 2.0 fastness Fixer 4 OD 0.94 1.25 1.36 1.50 1.53 Smear 5.0 5.0 4.04.0 3.5 fastness Fixer 5 OD 0.94 1.01 1.24 1.48 1.58 Smear 5.0 4.0 4.03.5 3.5 fastness

The results in Table 3 and FIG. 1 show increase in OD when the fixer isprinted with the ink compared to OD when no fixer is printed with theink. For all fixers, OD continues to increase with a higher amount offixer printed. As demonstrated in FIG. 1, for fixer 4 and fixer 5, smearresistance rating does not decrease as sharply as for the comparativefixers (see Comp1, Comp 2 and Comp 3). In other words, at similar ODlevels, the fixers of this disclosure have better smear resistance.

What is claimed is:
 1. An ink set for ink jet printing, comprising: anink jettable ink and an ink jettable fixer ink; wherein said inkjettable ink comprises an aqueous colorant; and said ink jettable fixerink comprises: (i) a multivalent metal salt, wherein the metal isselected from the group consisting of divalent metal ions, trivalentmetal ions, and mixtures thereof; and (ii) a salt stable, water soluble,predominantly non-ionic, polymeric binder, wherein said polymeric binderis a polyurethane comprising an ethylene oxide unit and has an averagenumber molecular weight of about 5000 to about 25,000; and wherein thepolymeric binder is substantially non-reactive with the colorant.
 2. Theink set of claim 1 wherein the colorant comprises a dye, a selfdispersed pigment or a pigment dispersion.
 3. The ink set of claim 2wherein the pigment dispersion comprises a pigment and an ionicallystabilized dispersant.
 4. The ink set of claim 1 wherein the fixer inkis substantially colorless.
 5. The ink set of claim 1 wherein thedivalent metal ions are selected from the group consisting of Ca²⁺,Cu²⁺, Ni²⁺, Mg²⁺, Zn²⁺ and Ba²⁺.
 6. The ink set of claim 1 wherein thetrivalent metal ions are selected from the group consisting of Al³⁺,Fe³⁺ and Cr³⁺.
 7. The ink set of claim 1 wherein the multivalent metalsalt is present in the amount of about 0.5% to about 15%, based on thetotal weight of the fixer ink.
 8. The ink set of claim 1 wherein thepolyurethane comprising an ethylene oxide unit comprises a nonioniccomponent.
 9. The ink set of claim 8 wherein the nonionic component isselected from the group consisting of ethylene oxide and ethylene oxidederivatives.
 10. The ink set of claim 1 wherein the polyurethanecomprising an ethylene oxide unit further comprises an ionic component.11. The ink set of claim 10 wherein the ionic component is an acid. 12.The ink set of claim 11 wherein the acid is dimethylolpropionic acid.13. The ink set of claim 1 wherein said polyurethane further comprises amethoxylated carboxylated polyallylamine having the chemical structure:

wherein n is an integer between 50 and
 200. 14. The ink set of claim 13wherein n is an integer between 100 and
 120. 15. The ink set of claim 13wherein the methoxylated carboxylated polyallylamine has a numberaverage molecular weight of about 5000 to about 25,000.
 16. The ink setof claim 1 wherein the salt stable, water soluble, predominantlynon-ionic, polymeric binder is present in the amount of about 0.5% toabout 10%, based on the total weight of the fixer ink.
 17. The ink setof claim 1 wherein the fixer ink further comprises a surfactant.
 18. Theink set of claim 1 wherein the fixer ink further comprises an aqueousvehicle.
 19. The ink set of claim 1 wherein the methoxylatedcarboxylated polyallylamine has a number average molecular weight offrom about 7000 to about 25,000.
 20. A method for printing on asubstrate comprising: (a) providing an ink set, comprising an inkjettable ink and an ink jettable fixer ink; wherein said ink jettableink comprises an aqueous colorant; and said ink jettable fixer inkcomprises: (i) a multivalent metal salt, wherein the metal is selectedfrom the group consisting of divalent metal ions such as Ca²⁺, Cu²⁺,Ni²⁺, Mg²⁺, Zn²⁺ and Ba²⁺, trivalent metal ions, such as Al³⁺, Fe³⁺ andCr³⁺, and mixtures thereof; and (ii) a salt stable, water soluble,predominantly non-ionic, polymeric binder, wherein said polymeric binderis a polyurethane comprising an ethylene oxide unit and has an averagenumber molecular weight of about 5000 to about 25,000; wherein thepolymeric binder is substantially non-reactive with the colorant; (b)applying the ink jettable fixer ink to the substrate, and (c) applyingthe aqueous colorant containing ink jettable ink to the substrate.